The present invention relates in general to centrifuges and more particularly to an arrangement designed to prevent an ultracentrifuge rotor from exceeding a relative speed which could result in a hazardous condition in the form of an uncontained explosion of the rotor.
Ultracentrifuges are generally intended for laboratory use and the rotor drive is designed to make available to the operator any one of many possible speeds of rotation. Several sizes and types of rotors are generally supplied to accommodate various types of work and different rotational speeds. Thus, one rotor may be adapted for one type of separating work and designed for speeds ranging up to 20,000 R.P.M., and another designed for higher speeds which may, for example, range up to 40,000 R.P.M. and another up to 50,000 R.P.M. There is always the possibility that an attendant may select the wrong rotor for the speed of operation selected for the centrifuge with the result that the safe speed of operation for the particular rotor is exceeded.
Because of the high rotative speeds employed in ultracentrifuge equipment, it is not possible to design all of the rotors employed with the centrifuge with a safety factor as high as might normally be considered good engineering practice and, therefore, it is necessary to guard against excessive rotative speeds. Excessive speed may cause a rotor to burst or "explode" into a multitude of fragments and in the event of extremely high rotative energy forces, it is possible that some of these fragments may not be contained within the centrifuge housing and could likely injure an attendant or do great damage to the surrounding laboratory. It is desirable, therefore, to prevent the rotor from attaining a rotative speed at which such high energy is created.
In most instances, an electronic or electromechanical overspeed control means is included as part of the centrifuge or rotor and this will normally prevent a particular rotor from exceeding its designed speed. Examples of such safety devices are disclosed in U.S. Pat. Nos. 2,666,572 and 3,101,322 both of which are assigned to Beckman Instruments, Inc., the assignee of the present invention. Another arrangement for protecting against an overspeed condition is disclosed in patent application Ser. No. 458,837, filed in the name of Herschel E. Wright and assigned to Beckman Instruments, Inc., the assignee of the present invention. There is, however, always the possibility that the electronic, electromechanical or mechanical overspeed control may fail to function properly and thereby permit the rotor to be driven at an excessive speed. The present invention is an improvement over other type devices and provides a further or redundant measure of safety control over and above the normal type of overspeed control apparatus in order to prevent the occurrence of a hazardous explosive condition.